The invention relates to a process for producing an adsorption unit, to a retooling process for an adsorption unit, and to an adsorption unit produced by the production process.
In industrial plants, there is frequent use of apparatuses for prepurification by means of adsorption, for example for drying large fluid volumes, which feature a high throughput. For example, in cryogenic air fractionation plants, water, CO2 and further trace impurities are separated from raw air in such apparatuses, in order that these impurities do not condense and hence lead to problems in downstream process steps, especially compression and cooling.
Typically, for this purpose, radial adsorbers, for example, are used, since these are suitable for large flow volumes. These are frequently of cylindrical construction, wherein the fluid to be cleaned flows through a hollow cylinder filled with a bed of an adsorbent from the inside outward or from the outside inward.
EP 0 402 783 A2 describes a radial adsorber of this kind, in which a reactor housing is of essentially cylindrically symmetric construction about a vertical axis.
The adsorbent frequently comprises regular bodies or particles having a defined size, for example beads having a diameter of a few millimetres. The individual adsorbent particles are subjected to mechanical stress by adsorption, which is also called loading, since they swell, for example, and/or the heat of adsorption released causes thermal stresses in the material. Stresses likewise occur in the regenerating of the particles, since the particles contract, for example. In cyclical operation of an adsorption unit, this can lead to breakup of the particles. The fragments of the particles can be discharged, for example, through the orifices in the inner or outer basket.
Overall, this can reduce the adsorption capacity of the radial adsorber. In addition, it can lead to formation of a region in the hollow cylinder without adsorbent, through which the fluid can flow through the radial adsorber in uncleaned form. Then the bed has to be replenished again, in order to maintain the drying properties of the radial adsorber. This can result in frequent and unplanned shutdowns of an industrial plant.
Against this background, one problem addressed by the invention is that of providing a process for producing an improved adsorption unit.